Fortran關係運算符

下表列出了所有的Fortran支持的關係運算符。假設變量A=10和變量B=20，則：

操作符

等同

描述

示例

==

.eq.

檢查兩個操作數的值相等與否，如果是，則條件變爲真。

(A == B) i不爲 true.

/=

.ne.

檢查，兩個操作數的值相等與否，如果值不相等，則條件變爲真。

(A != B) 爲 true.

>

.gt.

檢查，左操作數的值大於右操作數的值，如果是的話那麼條件爲真。

(A > B)不爲true.

<

.lt.

檢查，左操作數的值是否小於右操作數的值，如果是的話那麼條件爲真。

(A < B) 是 true.

>=

.ge.

檢查，左邊的操作數的值是否大於或等於右操作數的值，如果是，則條件變爲真。

(A >= B) 不爲 true.

<=

.le.

檢查，左邊的操作數的值是否小於或等於右操作數的值，如果是，則條件變爲真。

(A <= B) 爲 true.

示例

試試下面的例子就明白所有在Fortran語言可用的邏輯運算符：

program logicalOp ! this program checks logical operators implicit none ! variable declaration
logical :: a, b ! assigning values
a = .true. b = .false. if (a .and. b) then print *, "Line 1 - Condition is true" else print *, "Line 1 - Condition is false" end if if (a .or. b) then print *, "Line 2 - Condition is true" else print *, "Line 2 - Condition is false" end if ! changing values
a = .false. b = .true. if (.not.(a .and. b)) then print *, "Line 3 - Condition is true" else print *, "Line 3 - Condition is false" end if if (b .neqv. a) then print *, "Line 4 - Condition is true" else print *, "Line 4 - Condition is false" end if if (b .eqv. a) then print *, "Line 5 - Condition is true" else print *, "Line 5 - Condition is false" end if end program logicalOp

當編譯並執行上述程序,將產生以下結果：

Line 1 - Condition is false
Line 2 - Condition is true
Line 3 - Condition is true
Line 4 - Condition is true
Line 5 - Condition is false